1. Field of the Invention
The present invention relates to an image sensing apparatus such as a digital camera or digital video camera and, more particularly, to an image sensing apparatus preferably used to take a motion image by using an autofocus function.
2. Description of the Related Art
Some image sensing apparatuses such as a digital camera and digital video camera comprise an automatic focusing function of automatically focusing the camera on an object. The automatic focusing function is called an “autofocus function” or “AF function”. Digital cameras generally adopt a method of extracting the high-frequency component of a luminance signal obtained from a CCD (Charge Coupled Device) serving as an image sensing element, evaluating an in-focus position, and moving the photographing lens to a position at which the high-frequency component maximizes (see, e.g., Jpn. Pat. Appln. KOKAI Publication No. 3-285467).
With an image sensing apparatus having the above-mentioned automatic focusing function, the user can easily obtain an in-focus image in photographing without any consciousness. However, the conventional autofocus method searches for an in-focus position by moving the photographing lens forward and backward along the optical axis, as disclosed in Jpn. Pat. Appln. KOKAI Publication No. 3-285467. If a motion image is taken (recorded), an out-of-focus image is recorded during search for the in-focus position.